1. Field of the Invention
The present invention relates to a plane display device.
2. Description of the Related Art
A plane display device (having a flat panel form) is variously examined as an image display device which can substitute for a cathode-ray tube (CRT). A liquid crystal display device (LCD), an electroluminescence display device (ELD), and a plasma display device (PDP) can be exemplified as such a plane display device. In addition, the development of a plane display device having electron emitting elements incorporated therein is also carried out. Here, a cold cathode field electron emitting element, a metal/insulating film/metal type element (called an MIM element as well), and a surface-conduction type electron emitting element are known as the electron emitting element. The plane display device having such an electron emitting element incorporated therein as an electron emitting source receives the attention from a viewpoint of a high resolution, color display with a high luminance, and low power consumption.
The cold cathode field emission display device (may be hereinafter simply abbreviated as “the display device”) as the plane display device having the cold cathode field emitting elements incorporated therein as the electron emission source generally has a construction in which a cathode panel and an anode panel are disposed so as to face each other through a space kept at a vacuum. Here, the cathode panel has an electron emitting area corresponding to pixels (sub-pixels in the case of the color display) arranged in two-dimensional matrix. Also, the anode panel has phosphor layers which are excited through collision of electrons emitted from the electron emitting areas therewith, thereby emitting lights. Normally, one or plural cold cathode field emission elements (may be abbreviated hereinafter as “the field emission element”) are provided in the plane display device. A spindt type field emission element, a flat type field emission element, an edge type field emission element, a plane type field emission element, and the like can be given as the field emission element.
FIG. 8 is a conceptual partial end view of a related art display device having a spindt type field emission element as an example. FIG. 9 is a schematic exploded perspective view of parts of a cathode panel CP and an anode panel AP when the cathode panel CP and the anode panel AP are exploded.
In order to maintain the degree of vacuum of a space defined between the cathode panel CP and the anode panel AP, a getter 62 made of a material which can get a residual gas within the space is disposed in such a display device. The getter 62 is normally disposed in a non-effective area (a frame-like area surrounding an effective area) of at least one of the cathode panel CP and the anode panel AP. In the example shown in FIG. 8, one or plural through holes 61 (one through hole 61 in the example shown in FIG. 8) are provided in the cathode panel CP. A getter box 60 which, for example, is made of a glass is mounted to a supporting body 10 so as to close up the through hole 61 from the outside of the cathode panel CP. Also, the getter 62 is accommodated in the getter box 60. Another through hole 50 for evacuation is provided in another portion of the non-effective area. An exhaust tube 51, called a tip tube as well, which is sealed after the evacuation is mounted to the through hole 50.
The spindt type field emission element constituting this display device includes cathode electrodes 11, an insulating layer 12, gate electrodes 13, opening portions 14 (each having a first opening portion 14A provided in each of the gate electrodes 13, and a second opening portion 14B provided in the insulating layer 12), and conical electron emitting portions 15. Here, the cathode electrodes 11 are formed on the supporting body 10. The insulating layer 12 is formed on the supporting body 10 and each of the cathode electrodes 11. The opening portions 14 are formed in each of the gate electrodes 13, and the insulating layer 12. Also, each of the conical electron emitting portions 15 is formed on a corresponding one of the cathode electrodes 11 located in a bottom portion of corresponding one of the opening portions 14.
In this display device, each of the cathode electrodes 11 extends in a first direction (in a Y direction in FIGS. 8 and 9). Each of the gate electrodes 13 extends in a second direction (in an X direction in FIGS. 8 and 9) different from the first direction. In general, the cathode electrodes 11 and the gate electrodes 13 are formed in strip shapes in the directions, respectively, along which projected images of the cathode electrodes 11 and the gate electrodes 13 intersect each other perpendicularly. Overlap areas in which the strip-shaped cathode electrodes 11 and the strip-shaped gate electrodes 13 overlap each other are electron emitting areas EA, respectively. Each of the electron emitting areas EA corresponds to an area for one sub-pixel. Also, such electron emitting areas EA are normally arranged in a two-dimensional matrix within the effective area (an area corresponding to a display area of the display device) of the cathode panel CP.
On the other hand, phosphor layers 22 (more specifically, a red emission phosphor layer 22R, a green emission phosphor layer 22G, and a blue emission phosphor layer 22B) having a predetermined pattern are formed on the substrate 20. Thus, the anode panel AP has a structure in which the phosphor layers 22 are covered with the anode electrode 24. Note that, a space defined between the adjacent phosphor layers 22 is filled with a light absorbing layer (black matrix) 23 made of a light absorbing material such as carbon. As a result, color turbidity and an optical crosstalk of the displayed image are prevented from being generated. In FIG. 8, reference numeral 21 designates a partition wall, reference numeral 40 designates a spacer, for example, having a plate-like shape, and reference numeral 25 designates a spacer holding portion. Also, reference numeral 26 designates a joining member made of a joining material such as a frit glass, a reference numeral 16 designates an interlayer insulating layer, and reference numeral 17 designates a converging electrode. Note that, illustrations of the partition walls, the spacers, the spacer holding portion, the converging electrode, and the interlayer insulating layer are omitted in FIG. 9 for the sake of simplicity.
The anode electrode 24 has an antistatic function for the phosphor layers 22 in addition to a function as a reflecting film for reflecting lights emitted from the phosphor layers 22, respectively. In general, the electrons recoiling from the phosphor layers 22, or the secondary electrons emitted from the phosphor layers 22 collide with other phosphor layers 22, so that the so-called optical crosstalk (color turbidity) occurs. In order to avoid this situation, the partition wall 21 has a function of preventing the optical crosstalk from being generated.
One sub-pixel is constituted by the electron emitting area EA on the cathode panel side, and the phosphor layer 22, on the anode panel side, facing the electron emitting area EA. In the case of the color display device, one pixel is constituted by a set of one red emission phosphor layer, one green emission phosphor layer, and one blue emission phosphor layer. Such pixels, for example, are arranged on the order of several hundreds of thousands to several millions in the effective area.
Also, the anode panel AP and the cathode panel CP are disposed so that the electron emitting areas EA face the phosphor layers 22, respectively, and are joined to each other through the joining member 26 in their peripheral portions. After that, air in the space defined among the anode panel AP, the cathode panel CP and the joining member 26 is exhausted, and the space defined thereamong is sealed. As a result, the display device can be manufactured. In this case, the space defined among the anode panel AP, the cathode panel CP and the joining member 26 is kept at a high vacuum (for example, equal to or lower than 1×10−3 Pa).
A cathode electrode controlling circuit 31 applies a relatively negative voltage to each of the cathode electrodes 11. A gate electrode controlling circuit 32 applies a relatively positive voltage to each of the gate electrodes 13. A converging electrode controlling circuit (not shown) applies a relatively negative voltage (for example, 0 V) to each of the converging electrodes 17. Also, an anode electrode controlling circuit 33 applies a higher positive voltage than that applied to each of the gate electrodes 13 to the anode electrode 24. When a desired image is displayed on such a display device, for example, the cathode electrode controlling circuit 31 inputs a scanning signal to each of the cathode electrodes 11, and the gate electrode controlling circuit 32 inputs a video signal corresponding to the desired image to each of the cathode electrodes 13. Alternatively, the cathode electrode controlling circuit 31 inputs a video signal corresponding to the desired image to each of the cathode electrodes 11, and the gate electrode controlling circuit 32 inputs a scanning signal to each of the gate electrodes 13. Electrons are emitted from the electron emitting portions 15 in accordance with the quantum tunneling effect caused by electric fields generated when voltages are applied across the cathode electrodes 11 and the gate electrodes 13, respectively. The anode electrode 24 attracts the electrons thus emitted, so that the electrons penetrate the anode electrode 24 to collide with the corresponding phosphor layers 22, respectively. As a result, the phosphor layers 22 are excited to emit lights, respectively, thereby enabling a desired image to be obtained. In other words, the operation of the cold cathode field electron emission display device is basically controlled in accordance with the voltage applied to each of the gate electrodes 13, and the voltage applied to each of the cathode electrodes 11.
As has been described above, the high positive voltage is applied to the anode electrode 24. Therefore, the anode electrode 24 and the anode electrode controlling circuit 33 must be electrically connected to each other with a highly reliable structure. For example, a plane display device described in Japanese Patent Laid-Open No. Hei 5-114372 uses a feeding terminal which is disposed so as to contact an anode electrode through a hole portion formed in a cathode panel. More specifically, the plane display device described in Japanese Patent Laid-Open No. Hei 5-114372 includes a chip tube as a sealing body, and a fluorescent screen feeding terminal. In this case, the fluorescent screen feeding terminal is constituted by two parts having an elastic body and a terminal deriving portion. Also, one end of the terminal deriving portion extends completely through the sealing body 18 to protrude to the outside.